More than 500 employees of OpenAI have threatened to leave the company if the current board doesn’t resign and reinstate former Chief Executive Sam Altman and former President Greg Brockman.

The threat was made in a letter to the board of directors and among the signees was Ilya Sutskever, the company’s chief scientist and one of the members of the four-person board that voted to oust Altman. OpenAI currently has about 770 workers.